Strings, f-strings, and t-strings

A Python string is an immutable sequence of Unicode characters. Every method on it returns a new string; nothing modifies one in place. Bytes are a separate type, and the boundary between the two, encode and decode, is exactly where HTTP bodies, files, and model responses cross into your program. Most of the string work in a backend is formatting: putting a ticket id, a customer name, and a model's answer into a message with the right shape. Python has had several ways to do that, and since 3.6 the answer is the f-string.

Python 3.14 adds a sibling, the t-string. It looks like an f-string with a t prefix, but instead of producing text it produces a Template object holding the literal parts and the interpolated values separately. That separation is the point. When the value is customer text going into a prompt, a SQL query, or an HTML page, you want to decide how it is escaped before it is joined, and an f-string has already joined it by the time you can look.